Locking device for office chairs and the like

ABSTRACT

Locking device ( 1 ) for office chairs and the like comprising of a first locking element ( 9 ) operatively associable to a base unit ( 3 ) of a chair and a second locking element ( 10 ) operatively associable at least to a revolving portion ( 6 ) of the chair. The first and second locking elements ( 10 ) are selectively associable in an active position to lock the rotation of the revolving portion ( 6 ) in respect to a base unit ( 3 ) and detachable in a passive position to unlock such rotation. The shifting between the active position and the passive position takes place along a shifting direction ( 11 ) substantially perpendicular to the contrasting force developing between the locking elements ( 9, 10 ) in active position. The shifting direction ( 11 ) is also substantially perpendicular to the components of the contrasting force, tangential and perpendicular to the contact surfaces between the engaging portions ( 9   a   , 10   a ).

The present invention relates to a locking device for office chairs and the like. As it is known, office chairs generally present adjustable parts in height and tilt. These chairs might present the back, and sometimes also the seat or the frame, adjustable in tilt in respect to a base unit, for example of a box form, which is connected at the top end of an upright which defines the vertical support of the chair. The connection between the base unit and the upright is realized substantially through a frustum of cone element united to a base unit and fit to receive the top end of the upright. Particular mechanisms are known which can tilt the back only, which are called “at permanent contact”, mechanisms which allow the independent tilt of the back and seat which are called “asynchronous” type, and mechanisms which allow the simultaneous and proportional tilt, according to a predetermined ratio between the angles of the back and seat, which are called “synchronous” type. Mechanisms are also known with reclining back and seat and solid between them, called “swinging” type. In all the above mentioned cases elastic elements are provided to contrast the tilting and it is possible selectively to prevent the swing of the parts which can tilt through proper locking devices. Such locking devices are usually made of multiple slotting positions and by at least a locking element fit to engage selectively in such slotting positions to stop the swing of the tilting portions. The locking element is mobile at least between a front resting position which cooperates with the slots and a back resting position in which the swing is permitted. Such locking element is usually operatively associated to the back, but can be also associated to the seat, and in particular, in the asynchronous mechanism, a locking-element for the back and one for the seat could be envisaged. The known technique, briefly described above, presents some drawbacks. The known locking devices in fact generally allow the association for each tilt position, of a single locking element in a corresponding seat. This makes it necessary to realize the locking element and the unit which includes the slots in sufficiently resistant material, in order to avoid the risk of a structural failure of the same. Such locking devices can often also become rather cumbersome, and to guarantee the reciprocal receding and advancing of the looking elements and of the slots it is sometimes necessary to opportunely modify the structure of the swinging mechanism with a consequent bigger complication. It has also to be noted that, as in the mechanisms there is a frontal advancing and receding of the locking elements, the force resulting from the contact between such elements has a tangential component which can show a tendency to pull back the locking elements, and can therefore cause the accidental unlocking of the device. Such problematic issues require the necessity of very accurate designing of the locking device, with consequent higher costs of designing and realization of the said device. In this situation the technical task set at the base of the present invention is to invent a locking device for office chairs and the like to be in a good enough position to obviate substantially the problems mentioned. For the purpose of the said technical task it is an important aim of the invention to make a locking device for office chairs that offers a high degree of freedom in the designing of the locking device and of the relative positioning. Besides it is the aim of the invention to make a locking device for office chairs which assures a safe locking and that results in simple and fast realization. It is another aim of the invention to make a locking device for office chairs of a universal type that can be assembled without substantial modifications on all the types of mechanisms for chairs (for example swinging, synchronous, asynchronous and at permanent contact). Besides it is the aim of the invention to make a locking device which is particularly compact. It is finally the technical aim of the present invention to make a locking device for office chairs which is of a contained cost of production. The precise technical task and the aims specified are substantially obtained by a locking device for office chairs which is characterized in that it included one or more technical solutions which are claimed below. In the following there is, only as an indicative and not as a limitative example, the description of a preferred but not exclusive form of execution of a locking device according to the invention, illustrated in the enclosed drawings, in which:

FIG. 1 shows a prospective view of a locking device for office chairs according to the present invention;

FIG. 2 is a section on a lateral view of a tilting mechanism for an office chair including the locking device of FIG. 1;

FIG. 3 is part of a section of the device of FIG. 1, in an active operative position of locking, executed according to a horizontal plan;

FIG. 4 is an view analogous to that of FIG. 3 with the locking device in a passive operative position of locking;

FIG. 5 shows an alternative profile for a locking element;

FIG. 6 shows an alternative realization of the locking elements.

With reference to the mentioned figures, a locking device for office chairs and the like according to the invention is globally shown with reference No 1. The locking device 1 is advantageously applicable to a mechanism 2 for an office chair, which includes essentially a base unit 3 fit to engage, through a connecting element 4, to the top end of an upright 5 which defines the vertical support of the chair. On the base unit 3 at least a revolving portion 6 of the chair is hinged in a known way, for example an supporting element 7 of the back. The mechanism 2 includes also an supporting element 8 of a seat of a chair, mounted above the base unit 3. The device 1 is applicable in a manner similar to all the types of known mechanisms, and therefore to mechanisms at “permanent contact”, in which the supporting element of the seat is joined to the base unit and the only reclining part is the back, to mechanisms of “synchronous” type, in which the supporting element of the seat is associated in a revolving way to the base unit and to the supporting element of the back to swing proportionally to the swinging of the supporting element of the back and to mechanisms of “swinging” type, in which the element of support of the seat is fixed to the supporting element of the back to swing jointly with the same. The locking device can also be used in mechanisms of “asynchronous” type, in which the supporting element of the seat is associated in a revolving way to the base unit, to swing in an independent way in respect to the base unit. In such a case the mechanism includes a second locking device operatively placed between the supporting element of the seat and the base unit. Means of elastic support are usually also foreseen (not shown on the figures), such as a spring, placed between each turning portion in an independent way and the base unit, and therefore at least between the supporting element and base unit. The locking device 1 includes a first locking element 9 having a first portion of engagement 9 a mounted on the base unit 3, and a second locking element 10 having a second portion of engagement 10 a and mounted on the rotating portion 6. The first engagement portion 9 a and the second engagement portion 10 a are selectively associable in an active position to lock the rotation of the revolving portion 6 in respect to the base unit 3 and can dissociate in a passive position to unlock such rotation. When the device 1 is in a locking position, a contrasting force develops between the two engaging portions 9 a, 10 a and therefore between the two locking elements 9,10, due to the action created on the mobile portion by the means of elastic support, when the chair is not in use, and by the weight of the user when the chair is used. Such force, which has a tangential component to the contact's surfaces of the engaging portions 9 a, 10 a and a perpendicular component to such surfaces, is due to the rotary action acting in direction 12, on the second element 10, and is inclined to push back the first locking element 9 away from the second locking element 10. The contrasting force therefore lies in the plane in which has been executed the section of FIG. 2. In line with the present invention, the displacement between the active and the passive positions occurs along a displacement's direction substantially perpendicular to the contrasting force. Preferably such displacement besides is substantially perpendicular also to the tangential components and perpendicular to the contact surfaces between the engaging portions 9 a, 10 a. In this way the locking is much safer, because the displacement happens perpendicularly to the force which tends to distance the two locking elements 9, 10 and therefore such force cannot separate such elements 9, 10. The direction of the displacement is shown in FIG. 1 with the reference number 11. Advantageously the displacement could be a lateral displacement relative to the first 9 a and to the second 10 a portion of engagement. For lateral displacement it is understood a displacement in a transversal direction and preferably perpendicular to a vertical plane passing centrally on both the first 9 and on the second locking element 10, when these are in active position. Advantageously, besides, the displacement substantially happens perpendicularly to the direction of the frontal distancing between the engaging portions 9 a, 10 a. In the active position the first 9 a and second 10 a engaging portions are reciprocally faced in correspondence to a contact surface. Advantageously the displacement between the active position and the passive position takes place along a direction of displacement and shift parallel to the surface of contact. Preferably also the displacement between the active position and passive position takes place along a direction of movement substantially parallel to the rotating axis 13 of the revolving portion 6. In particular the first locking element 9 is translational in a lateral and parallel way to the surface of the engaging portion 9 a to lock selectively the rotation of the revolving portion 6, while the second locking element 10 is fixed to the revolving portion 6. The first locking element 9 consists preferably of a portion of a circular crown entirely toothed and cooperating with the second engaging portion 10 a. Advantageously the teeth are all cooperating contemporarily with the second engaging portion 10 a in the operative active position. Preferably the second locking element 10 is a wheel, at least partially toothed (FIG. 1) and therefore provided with a number of resting positions, in which the teeth can be inserted. The wheel is fixed to the revolving portion 6 to rotate jointly with it, according to the direction shown of FIGS. 1 and 2 with number 12, around the axis 13. The first 9 and second 10 locking elements could be provided with corresponding set of teeth having an involute, square and other type profile. In FIG. 5 is shown an example of a profile for an undercut toothed gear placed on the second element 10 but applicable in an analogue way and counter-shaped on the first element 9, which offers a further advantage to impede a frontal detachment of the locking elements, not requiring the presence of a containing element 21 for the first locking element. In an alternative embodiment, partially illustrated in FIG. 6 with only the locking elements, the first locking element 9 is provided with stopping elements, for example studs, on a lateral face, extending therefore in the shifting direction 11 of the same first element. The second element 10 is provided with proper stopping seats, such as shaped holes or the like, also these extending in the shifting direction 11 of the first locking element 9 to cooperate with the stopping elements of the first locking element 9. Also in that case there is a lateral shifting of the two locking elements 9, 10 which is acting in a perpendicular direction to the contrasting force developing between the faces of the holes and the locking elements. The device 1 includes also operating means 14 operatively connected to the first locking element 9 to execute the locking and unlocking of the device 1. The operating means 14 include a push rod 15 assembled in a revolving way on the base unit 3 and manually actionable, for example through a lever (not illustrated), on which is assembled the first locking element 9 in a translational way. The operating means 14 comprise also cam shaped means 16 operatively associated to the push rod 15 to convert the rotary movement of the push rod 15 in a translational movement of the first locking element 9 along the rod. The cam shaped means 16 include a small pivot 17 integral with and transversal to the push rod 15 and an operating element 18 freely and glidingly associated to the rod and provided with a cam track 19 in which the small pivot 17 is inserted. The cam track 19 is provided with a transferring central portion 19 a and of two end portions 19 b, 19 c, corresponding to the active and passive positions, which are slanted in respect to the transferring central portion 19 a in order to prevent the accidental slip of the operating element 18 when the locking is in an active and passive position. The operating means 14 include also an elastic element 20 connecting operatively the first locking element 9 and the second command element 18, to guarantee the functions of pre-selection and anti-shock of the locking. It could also be envisaged a containing element 21, for example a frame or a shifting guide, to support the first locking element 9 in the various operative positions and along its movement and to compensate the thrust of the contrasting force. Alternatively the operating means 14 could be foreseen to activate the second shifting locking element 10, with a first fixed locking element 9. As illustrated in FIG. 2 the device 1 includes two first locking elements 9, 9′ and two second locking elements 10, 10′ assembled on the push rod 15. Such elements are symmetrically positioned on opposite sides of the revolving portion 6 to avoid loss of balance of the revolving portion 6 in locking position and are respectively cooperating to block the rotation of the revolving portion 6. The mechanism 2 includes a device to adjust the height of the chair, which is itself not described as it is a known type. The locking device 1 described above could therefore be applied to any chair having reclining portions, which is usually provided with a back, fixed to the supporting element 7 of the back, of a seat, fixed to an supporting element 8 of the seat, of a vertical upright resting on a base, and eventually of arms for the support of the upper body of the user. The functioning of a locking device, above described in a prevalently structural sense, is the following. When the device 1 is in passive position (FIG. 4), the revolving portion can oscillate constrained by the means of elastic support. When the push rod 15 is rotated in the direction 22, around the axis 23, to operate the locking, the small pivot 17 runs inside the cam track 19 of the operating element 18, making the same move along the push rod 15 towards the first locking element 9. The elastic element 20 is therefore compressed and pushes the first locking element 9 towards the second locking element 10. If the second locking element 10 is situated with the resting seats in line with the teeth of the first locking element 9, the device 1 goes immediately into active position (FIG. 3). If that is not the case, the device finds itself in pre-selection, and as soon as the revolving portion 6 is rotated in a proper angular position, the first locking element 9 is pushed together with the second locking element 10 and activates the locking. When one wants to unlock the device 1, one proceeds in the opposite way, rotating the push rod 15 in the opposite direction. The small pivot 17 pushes therefore the operating element 18 in the opposite direction to the first locking element 9, putting in traction the elastic element 20. If the user is resting on the revolving portion 6, the first locking element 9 cannot yet shift in respect to the second element 10 and unlock the rotation, but when the weight on the revolving portion 6 is lightened, the first locking element 9 is pulled by the elastic element 20 and the device moves in a passive position. Such functioning is known as anti-collision or anti-shock. Obviously, when the locking device 1 is in an unlocking position, the tilting portion of the chair is free to recline under the weight of the user seated on the chair and the means of elastic support exercise a suitable contrast force. When the locking device 1 is in a locking position, the swinging is impeded. The invention achieves important advantages. In fact, a locking device according to the present invention offers a good deal of freedom in designing the locking device and of the relative positioning. Besides such device assures a secure locking of the swinging with the result of being particularly compact. Besides it has to be underlined that the locking device for office chairs results in a simple and fast realization. In the end it has to be noted that a device according to the present invention presents reduced costs of production and allows also to use materials of relatively little resistance for the locking elements. Naturally several modifications and variations could be made to the device according to the present invention without digressing from the inventive concept which characterized it. All the items are replaceable with other technically equivalent elements and in practice all the materials used, and also the dimensions, could be of any type according to the need. 

1. Locking device (1) for office chairs and the like comprising: a first locking element (9) having a first engaging portion (9 a) and operatively associable to a base unit (3) of a chair; a second locking element (10) having a second engaging portion (10 a) and operatively associable at least to a revolving portion (6) of the chair, pivoted on the said base unit (3) of the chair, said first engaging portion (9 a) and said second engaging portion (10 a) being selectively associable in an active position to lock the rotation of the revolving portion (6) in respect to the base unit (3) and dissociable in a passive position to unlock such rotation, said first and second engaging portions (9 a, 10 a) being reciprocally faced in said active position to exchange a contrasting force between each other, the shifting between said active position and said passive position taking place along a shifting direction (11) substantially perpendicular to said contrasting force, characterized in that at least one of said first and second locking elements (9, 10) is mobile in said shifting direction (11) in a parallel way to the surface of its own engaging portion (9 a, 10 a).
 2. Device according to claim 1 characterized in that said shifting direction (11) is substantially perpendicular also to the components, of said contrasting force, tangential and perpendicular to the contact surfaces between the engaging portions 9 a, 10 a.
 3. Device according to claim 1 characterized in that the shifting between said active position and said passive position takes place through a relative lateral displacement of said first and second engaging portions (9 a, 10 a).
 4. Device according to claim 1, characterized in that first and second engaging portions (9 a, 10 a) are reciprocally faced in said active position in correspondence of a contact surface, said shifting direction (11) being substantially parallel to said contact surface.
 5. Device according to claim 1, characterized in that said shifting direction (11) is substantially parallel to the rotating axis (13) of the revolving portion (6).
 6. Device according to claim 1, characterized in that said second locking element (10) is fixed to said revolving portion (6) and said first locking element (9) is assembled in a translational way on said base unit (3).
 7. Device according to claim 1, characterized in that said second engaging portion (10 a) is provided with a number of resting seats, said first engaging portion (9 a) being selectively associable with said engaging seats.
 8. Device according to claim 1, characterized in that said second locking element (10) is a wheel at least partially toothed.
 9. Device according to claim 1, characterized in that said first locking element (9) is provided with a number of teeth cooperating with said second engaging portion (10 a).
 10. Device according to claim 9, characterized in that said teeth are all cooperating contemporarily with said second engaging portion (10 a) in said active operative position.
 11. Device according to claim 1, characterized in that said first locking element (9) is constituted by a portion of a circular crown completely toothed and cooperating with said second engaging portion (10 a).
 12. Device according to claim 1, characterized in that it includes two of said first locking (9, 9′) and two of said second locking elements (10, 10′) respectively cooperating to lock the rotation of said revolving portion and suitably placed on opposite sides of the revolving portion (6) to avoid the unbalancing of the revolving portion (6) in locking position.
 13. Device according to claim 1, characterized in that it includes also operating means (14) operatively connected to said first locking element (9) to operate the locking and the unlocking of the device (1).
 14. Device according to claim, characterized in that said operating means (14) are common to the said two first locking elements (9, 9′).
 15. Device according to claim 13, characterized in that said operating means (14) include a push rod (15) assembled in a revolving way on said base unit (3) and driven manually, on which is assembled in a translational way said first locking element (9).
 16. Device according to claim 15, characterized in that said operating means (14) include also cam shaped means (16) operatively associated to said push rod (15) to convert the rotary movement of the push rod (15) in a translational movement of the first locking element (9) along the rod (15).
 17. Device according to claim 16, characterized in that said cam means (16) include a small pivot (17) integral with and transversal to said rod (15) and an operating element (18) associated in a moving way to said rod (15) and provided with a cam track (19) in which is inserted the said small pivot (17).
 18. Device according to claim 17, characterized in that said cam track (19) is provided with a central transferring portion (19 a) and of two end portions (19 b, 19 c), corresponding to said active and passive positions, said end portions (19 b, 19 c) having substantially a perpendicular development to said shifting direction (11) to impede the accidental shifting of the command element (18) when the locking is in active and passive position.
 19. Device according to claim 17, characterized in that it includes also an elastic element (20) operatively connecting said first locking element (9) and said second operating element (18), to provide for the functions of pre-selection and anti-shock of the locking.
 20. Device according to claim 1, characterized in that it includes also a containing element (21) to hold said first locking element (9) in the various operative positions.
 21. Device according to claim 1, characterized in that said first and second locking elements (10) are provided with a corresponding set of gear teeth having an involute profile.
 22. Device according to claim 1, characterized in that the said first and second locking element (10) are provided with a corresponding set of gear teeth having an undercut profile.
 23. Device according to claim 1, characterized in that said first engaging portion (9 a) and said second engaging portion (10 a) are parallel to the shifting direction (11).
 24. Device according to claim 23, characterized in that said first engaging portion (9 a) and said second engaging portion (10 a) are provided with resting seats and with corresponding resting teeth developing perpendicularly to the shifting direction (11).
 25. Device according to claim 1, characterized in that said first engaging portion (9 a) and said second engaging portion (10 a) are perpendicular to the shifting direction (11).
 26. Device according to claim 25, characterized in that said first engaging portion (9 a) and said second engaging portion (10 a) are provided with resting seats and with corresponding resting elements developing parallel to the shifting direction (11).
 27. Mechanism (2) for office chairs and the like, comprising of: a base unit (3) fit to engage, through a connecting element (4), at the top end of an upright (5) which defines the vertical support of the chair, a supporting element (7) of a back of the chair engaged in a revolving way to said base unit (3), a supporting element (8) of a seat of a chair mounted above said base unit (3), means of elastic support placed at least between said supporting element (7) and said base unit (3), characterized in that it includes a locking device (1) according to claim 1, to lock selectively the swinging of at least said supporting element (7) of the back in respect to said base unit (3).
 28. Mechanism according to claim 27, characterized in that said supporting element (8) of the seat is swively associated to the base unit (3) to swing in respect to the base unit (3) in an independent way from said supporting element (7) of the back and by the fact to include also a second locking device (1), according to claim 1, operatively placed in between said supporting element (8) of the seat and said base unit (3), said means of elastic support being provided also between said supporting element (8) of the seat and said base unit (3).
 29. Chair characterized in that it includes a locking device (1) according to claim
 1. 30. Chair characterized in that it includes a mechanism (2) according to claim
 27. 